Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$103.93	9.714%	$114.0258	$114.03	$114.05	$114.00
Purchase #2	$34.55	11.707%	$38.5948	$38.59	$38.60	$38.60
Purchase #3	$51.83	4.294%	$54.0556	$54.06	$54.05	$54.10
Purchase #4	$114.44	4.230%	$119.2808	$119.28	$119.30	$119.30
Purchase #5	$140.29	5.654%	$148.222	$148.22	$148.20	$148.20
Purchase #6	$196.38	12.835%	$221.5854	$221.59	$221.60	$221.60
Purchase #7	$133.92	10.200%	$147.5798	$147.58	$147.60	$147.60
7 purchase totals =	$775.34		$843.3442	$843.35	$843.40	$843.40